Gulf of Mexico Deepwater Horizon Spill
Effects on Fish Revealed

Oil spill resulted in dramatic effects on
fish species in Louisiana marshes

Despite low concentrations of oil constituents in Gulf of Mexico waters from the Deepwater Horizon spill, fish were dramatically affected by toxic components of the oil. So found a team led by scientists Fernando Galvez and Andrew Whitehead of Louisiana State University (LSU). The researchers published their results in the journal Proceedings of the National Academy of Sciences (PNAS) [See Open Access Article].

Galvez, Whitehead and colleagues undertook a combined field and laboratory study. It showed widespread effects of the Deepwater Horizon oil spill on fish in Louisiana marshes. Gene expression in tissues of the fish studied--in this case killifish--was predictive of oil spill responses such as developmental abnormalities and death, say the biologists. "It also indicated impairment of fish reproduction," says Whitehead.

Contamination and minnow trap in Louisiana.Credit: Andrew Whitehead
"Joining remote-sensing of the spill with gene expression data from wild-caught killifish, these scientists have captured the effects of low-level exposure to pollutants on the long-term health of fish," says George Gilchrist, acting deputy director of NSF's Division of Environmental Biology, which funded the research. "It's a landmark study in applying genomic technology to wild animal populations under stress."

Fish gill tissues, important for maintaining critical fish body functions, appeared damaged and had altered protein expression. These effects persisted long after visible oil disappeared from a marsh's surface. Developing fish embryos exposed to field-collected waters had similar cellular responses, Whitehead says.

"This is of concern because early life-stages of many organisms are particularly sensitive to the toxic effects of oil," says Whitehead, "and because marsh contamination occurred during the spawning season of many species."

A major message of the previous Exxon Valdez oil spill in Alaska, he says, "is that sub-lethal biological effects, especially those linked with reproduction, are most predictive of the long-term effects of oil in many fish species, such as herring and salmon."

The Gulf of Mexico study shows similar early signals of sub-lethal effects after the Deepwater Horizon oil spill. The scientists are following up with research examining more direct effects of oil exposure on fish reproduction, development and growth.

Other co-authors of the paper are Benjamin Dubansky, Charlotte Bodinier, Scott Miles, Chet Pilley, Vandana Raghunathan, Jennifer Roach, and Nan Walker of LSU; Tzintzuri Garcia and Ronald Walter of Texas State University and Charles Rice of Clemson University.

The research was also funded by the Gulf of Mexico Research Initiative.